I don’t feel like I can post about issues with siblings or in laws or about raising kids if I think my brother or kids will read it. It’s not ‘secret’, but I wouldn’t have those talks with other adults with them in the room. Especially on threads regarding chinuch or major mess ups by their school system. I certainly would not have those talks in front of my children, (nobody should). If I could have anonymous screen name for ‘adult conversations’ and a different for ‘regular’ coffee breaks, I would do that.
So the nightmare would be . . . having acquaintances find out things that are better left unsaid unless anonymous. (Like the comments that start -‘One of my sisters hurt me very much yesterday. . .’ That’s fine as long as nobody can figure out who you are talking about)